Pre

并发编程-12线程安全策略之常见的线程不安全类

模拟SimpleDateFormate线程安全问题

package com.artisan.java8.testDate;import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.time.*;
import java.time.format.DateTimeFormatter;
import java.time.temporal.ChronoField;
import java.util.Date;/*** @author 小工匠* @version 1.0* @description: TODO* @date 2021/3/5 0:22* @mark: show me the code , change the world*/
public class DateInJava8 {public static void main(String[] args) throws ParseException, InterruptedException {Date date = new Date();System.out.println(date);/***  模拟SimpleDateFormat 的线程安全问题**  Exception in thread "Thread-30" java.lang.NumberFormatException: multiple points**  Exception in thread "Thread-24" java.lang.NumberFormatException: For input string: "E.250214E4"**/SimpleDateFormat sdf = new SimpleDateFormat("YYYY-MM-dd");for (int i = 0; i < 100; i++) {new Thread(() -> {for (int j = 0; j < 20; j++) {try {String format = sdf.format(date);Date d = sdf.parse(format);System.out.println(d);} catch (ParseException e) {e.printStackTrace();}}}).start();}}}

LocalDate

https://nowjava.com/docs/java-api-11/java.base/java/time/LocalDate.html

LocalDate 是final修饰的不可变类并且是线程安全的.

Java LocalDate is immutable class and hence thread safe.
LocalDate provides date output in the format of YYYY-MM-dd.
The LocalDate class has no time or Timezone data. So LocalDate is suitable to represent dates such as Birthday, National Holiday etc.
LocalDate class implements Temporal, TemporalAdjuster, ChronoLocalDate and Serializable interfaces.
LocalDate is a final class, so we can’t extend it.
LocalDate is a value based class, so we should use equals() method for comparing if two LocalDate instances are equal or not.

 public static void testLocalDate(){LocalDate x = LocalDate.now(); // 日期  2021-03-05System.out.println(x);LocalDate lo = LocalDate.of(2021,3,5);System.out.println(lo.getYear()); // 年  2021System.out.println(lo.getMonth()); // 月 MARCHSystem.out.println(lo.getDayOfMonth()); // 日 5System.out.println(lo.getDayOfYear()); // 一年中的第几天System.out.println(lo.getDayOfMonth());// 一个月中的第几天System.out.println(lo.getDayOfWeek());// 礼拜几System.out.println(lo.get(ChronoField.DAY_OF_MONTH));}

LocalTime

LocalTime provides time without any time zone information. It is very much similar to observing the time from a wall clock which just shown the time and not the time zone information.
The assumption from this API is that all the calendar system uses the same way of representing the time.
It is a value-based class, so use of reference equality (==), identity hash code or synchronization on instances of LocalTime may have - unexpected results and is highly advised to be avoided. The equals method should be used for comparisons.
The LocalTime class is immutable that mean any operation on the object would result in a new instance of LocalTime reference.

private static void testLocalTime() {LocalTime time = LocalTime.now();System.out.println(time.getHour());System.out.println(time.getMinute());System.out.println(time.getSecond());}

LocalDateTime

Java LocalDateTime is an immutable class, so it’s thread safe and suitable to use in multithreaded environment.
LocalDateTime provides date and time output in the format of YYYY-MM-DD-hh-mm-ss.zzz, extendable to nanosecond precision. So we can store “2017-11-10 21:30:45.123456789” in LocalDateTime object.
Just like the LocalDate class, LocalDateTime has no time zone data. We can use LocalDateTime instance for general purpose date and time information.
LocalDateTime class implements Comparable, ChronoLocalDateTime, Temporal, TemporalAdjuster, TermporalAccessor and Serializable interfaces.
LocalDateTime is a final class, so we can’t extend it.
LocalDateTime is a value based class, so we should use equals() method to check if two instances of LocalDateTime are equal or not.
LocalDateTime class is a synergistic ‘combination’ of LocalDate and LocalTime with the contatenated format as shown in the figure above.

    private static void testLocalDateTime() {LocalDate localDate = LocalDate.now();LocalTime time = LocalTime.now();LocalDateTime localDateTime = LocalDateTime.of(localDate, time);System.out.println(localDateTime.toString());LocalDateTime now = LocalDateTime.now();System.out.println(now);}

Instant

    private static void testInstant() throws InterruptedException {Instant start = Instant.now();Thread.sleep(1000L);Instant end = Instant.now();Duration duration = Duration.between(start, end);System.out.println(duration.toMillis());}

Period

    private static void testPeriod() {Period period = Period.between(LocalDate.of(2020, 5, 10),LocalDate.of(2021, 3, 4));System.out.println(period.getYears());System.out.println(period.getMonths());System.out.println(period.getDays());}

Duration

private static void testDuration() {LocalTime time = LocalTime.now();System.out.println(time);LocalTime beforeTime = time.minusHours(2);System.out.println(beforeTime);Duration duration = Duration.between(beforeTime,time );System.out.println(duration.toHours());}

format

    private static void testDateFormat() {LocalDate localDate = LocalDate.now();String format1 = localDate.format(DateTimeFormatter.BASIC_ISO_DATE);System.out.println(format1);DateTimeFormatter mySelfFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");String format = localDate.format(mySelfFormatter);System.out.println(format);}

parse

  private static void testDateParse() {String date1 = "20210305";LocalDate localDate = LocalDate.parse(date1, DateTimeFormatter.BASIC_ISO_DATE);System.out.println(localDate);DateTimeFormatter mySelfFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");String date2 = "2021-03-05";LocalDate localDate2 = LocalDate.parse(date2, mySelfFormatter);System.out.println(localDate2);}

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Java 8 - 时间API

文章目录

Pre

模拟SimpleDateFormate线程安全问题

LocalDate

LocalTime

LocalDateTime

Instant

Period

Duration

format

parse

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